Quasi-linear effects on the absorption of electron cyclotron waves by lower hybrid produced electron tails in tokamak plasmas

We study the time evolution of the absorption coefficient for extraordinary mode electron cyclotron waves interacting with a current-carrying electron distribution, in a tokamak plasma modelled by a plasma slab. The absorption coefficient is obtained from a numerical solution of the dispersion relation, which incorporates self-consistent effects due to the quasi-linear evolution of the electron distribution function, under the action of lower hybrid and electron cyclotron waves, and collisions. Our results show that for the whole plasma slab the asymptotic quasi-linear value of the absorption coefficient for electron cyclotron waves may be a few per cent larger than the coefficient due to absorption by the lower hybrid generated electron tail at the onset of the electron cyclotron waves, for sufficiently large angle of injection of these waves relative to the normal to the magnetic field.